This invention relates to a method and apparatus for flotation separation and more particularly to a method and apparatus for froth flotation separation and beneficiation of carbonaceous matter and mineral ores.
Froth flotation operates to separate finely ground valuable carbonaceous matter or minerals from their associated gangue. In general, the frothing process is carried out by introducing air into a pulp of finely divided carbonaceous matter or mineral ore in water containing a frothing or foaming agent whereby a froth is formed. The carbonaceous particles or minerals with a specific affinity for air bubbles rise to the surface in the froth and are thus separated from the gangue wetted by the water.
Conventional prior art processes for froth flotation separation of a slurry of particulate matter typically include those based on constructions wherein air is introduced into the liquid slurry of the particulate matter as, e.g., through a porous cell bottom or a hollow impeller shaft, thereby producing a surface froth.
Improved methods and apparatus for carrying out froth flotation separation of coal and other minerals are disclosed in U.S. Pat. No. 4,347,126 and U.S. Pat. No. 4,347,127. These patents disclose a flotation apparatus wherein a primary spray nozzle is positioned above the flotation tank for spraying input slurry, such as particulate coal or mineral ore into the tank and a recycle spray nozzle is positioned above the tank for respraying particulate matter collected in a collection trough positioned in the tank for collection sinking material.
In operation of the afore-described improved flotation method and apparatus, a froth is created on the liquid surface in the cell or tank in which a substantial quantity of desired particulate matter is floating. Typically, in order to remove the froth from tank or cell and thereby collect the froth, a skimming arrangement, e.g., skimmer plates, skim the froth on the liquid surface toward a discharge surface, typically upwardly inclined, extending from the liquid surface to a collection tank arranged at one side of the flotation apparatus. The skimmer plates skim the froth from the liquid surface up the inclined discharge surface and into the collection tank. A recognized problem associated with this type of skimming arrangement, however, is that the skimmers carry excessive undesirable mineral-laden water along with the froth which decreases the froth grade.